What PappaPeterPils has suggested also worked for me (S9) although even without restarting the phone. The essential steps were:
1. Turn NFC off still with the cover on.
2. Turn the screen off (or wait until it turns off automatically).
3. Remove the phone from the Clear view cover.
4. Unlock the phone and turn NFC on (I waited a minute or so just to make sure).
5. Put the cover back on while the screen is still active.
Had the same issue on the S10 with the clear view cover, in my case it was not switching to always on display when when closing the case and you could just see the home screen through the cover...
Glad to report after a full shutdown, 5 mins wait before powering back on and after that it appears to be working as expected... well almost, as it does not lock the phone when closed but think my S8 had the same issue since the Android 9 update